Gas, especially the liquefied propane gas, is widely used in our daily life for cooking purposes. However, the accidents causing loss of human lives and properties are always encountered. After analysing the accidental causes, it will be found that most of their reasons depend upon the continuous leaking of flammable gas. Whenever the burner flame is extinguished by the spillage of water overflowing from the cooking utensil on said burner, the unburned gas will be continuously emitted. The poisonous and uncolored gas may spread and accumulate in a space. If it meets any accidental spark, it will easily cause fire or explosion or it may cause asphyxiation of people. The present inventor has considered this dangerous phenomena, has developed the present safety device which will serve to save energy and prevent accidents.